One of the routes a lot of creationists take is to deny that evolution is a scientific theory. Why? They argue that a theory about origins could never be scientific because it isn't repeatable. Now how they do that and then on the other hand want ID or straight up biblical creationism presented to children is another question.
My question is this. What makes evolution a scientific theory? What makes a theory scientific? Is there is a straightforward criterion? Do intentions matter in science?
I don't think there is. We count a lot of things as science that we can't 'repeat' in the lab, such as astronomy. Throwing that out the window is foolish and ignores the enormous predictive power of these sorts of observationally based sciences.
Evolution is based not only on inference from the fossil record and other lines of evidence, but on direct observation of evolution happening in the lab and in nature and extrapolating that the same physical processes are at work. What evolution opponents really want is someone to produce a cat from a flea in the lab, or they won't be satisfied. That this is a ridiculous sort of request is precisely what they are counting on so that they can cling to their views. The fact is that evolution has made specific predictions, has falsifiability criteria, and involves a clear physical model of how it proceeds. ID has none of this.
So what counts as science? I think this is something that you know when you see it. It involves careful, quantitative reasoning about the world, an understanding of what counts as evidence for and against- with specific statistical analysis to be able to determine a probability of the model being true or false. There's a sense of a better theory making lots of specific predictions about how the world ought to look, and if it makes predictions about what we have not discovered yet, all the better. All of these things evolution has. The problem is, no matter how you form this there will be some exception to a part of the definition. I suggest using ID as a key example of a pseudo-science to help winnow out sloppy, unclear thinking from the sorts of scientific theories that will help us progress in our understanding of the world.
